The present invention relates to a novel polyurethane form having thermochromic properties and useful for toys, ornaments, bathing articles, kitchen utensils, industrial materials, etc. to give them a kind of temperature sensor function.
Many kinds of foams are commercially available. Of these, polyurethane foams are widely used for bedding, furniture, tools, vehicles, etc. as cushion materials, for buildings, machines, household electric appliances, etc. as heat-insulating materials, and also for toys, toiletware, sundries, etc. as water absorbing materials. These foams are colored as desired with usual dyes or pigments.
The polyurethane foam commercially used for toys, toiletware, sundries, etc. is in the form of cut pieces having the foam structure itself and is characterized in that it can be physically given various shapes. However, as far as colors are concerned, such a piece is merely given the color of a dye or pigment usually used as a coloring agent. Accordingly, if a commercial article is adapted to detect a change in the ambient temperature to exhibit a particular color in accordance with the change, for example, if a kitchen utensil is adapted to undergo a color change upon sensing temperature for the user to visually observe the temperature of hot water, the material so adapted will find important industrial use, but such polyurethane foam has not been disclosed.